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Topic Review
Mechanism of Organic Photovoltaics
The power conversion efficiencies (PCEs) of organic photovoltaics (OPVs) have reached more than 19%, along with the prosperous development of materials and device engineering. 
  • 351
  • 15 Jun 2023
Topic Review
Mechanism of Heterogeneous Alkaline Deacetylation of Chitin
Chitosan can be obtained from chitin chemically or by using enzymatic preparations. From a chemical point of view, both acids and alkalis can be used to deacetylate chitin. However, alkaline deacetylation is used more often since glycosidic bonds are very sensitive to an acidic environment, in which they are destroyed. A mechanism for the chitin deacetylation reaction is proposed, taking into account its kinetic features in which the decisive role is assigned to the effects of hydration. It has been shown that the rate of chitin deacetylation increases with a decrease in the degree of hydration of hydroxide ions in a concentrated alkali solution. When the alkali concentration is less than the limit of complete hydration, the reaction practically does not occur. Hypotheses have been put forward to explain the decrease in the rate of the reaction in the second flat portion of the kinetic curve. The first hypothesis is the formation of “free” water, leading to the hydration of chitin molecules and a decrease in the reaction rate. The second hypothesis postulates the formation of a stable amide anion of chitosan, which prevents the nucleophilic attack of the chitin macromolecule by hydroxide ions.
  • 864
  • 19 Jun 2023
Topic Review
Mechanism of Gadolinium-Based Contrast Agents Retention
The extracellular class of gadolinium-based contrast agents (GBCAs) is an essential tool for clinical diagnosis and disease management. The differences observed in tissue gadolinium retention and deposition associated with GBCAs administration is the direct consequence of the differing thermodynamic stability and kinetic inertness of GBCAs. 
  • 402
  • 10 Jan 2022
Topic Review
Mechanism of Diffusion Bonding
Critical aspects of innovative design in engineering disciplines like infrastructure, transportation, and medical applications require the joining of dissimilar materials. Welding and brazing, while widely used, may pose challenges when joining materials with large differences in melting temperature and can lead to mechanical property degradation. In contrast, diffusion bonding offers a lower temperature process that relies on solid-state interactions to develop bond strength. The joining of tungsten and steel, especially for fusion reactors, presents a unique challenge due to the significant disparity in melting temperatures and the propensity to form brittle intermetallics. Here, diffusion characteristics of tungsten–steel interfaces are examined and the influence of bonding parameters on mechanical properties are investigated. Additionally, CALPHAD modeling is employed to explore joining parameters, thermal stability, and diffusion kinetics. The insights from this research can be extended to join numerous dissimilar materials for specific applications such as aerospace, automobile industry, power plants, etc., enabling advanced and robust design with high efficiency.
  • 775
  • 17 Aug 2023
Topic Review
Mechanism of Cotton Combustion
As a cellulose-based polymer, the combustion of cotton is an exothermic oxidation process that takes place upon heating, consuming flammable gases, liquids, and solid residues produced during the pyrolysis of the textile material, thus generating heat.
  • 1.1K
  • 27 Jul 2023
Topic Review
Mechanism of Action of Thiazolidin-2,4-dione
The thiazolidin-2,4-dione (TZD) moiety plays a central role in the biological functioning of several essential molecules. The availability of substitutions at the third and fifth positions of the Thiazolidin-2,4-dione (TZD) scaffold makes it a highly utilized and versatile moiety that exhibits a wide range of biological activities.
  • 1.2K
  • 18 Oct 2022
Topic Review
Mechanism of Action of Tetrabromobisphenol A
Brominated flame retardants (BFR) have been extensively applied to reduce the flammability of some commercial products such as furniture, circuit boards, textiles, polystyrene foams, epoxy resins, and padding materials, because of their potency and ability to meet safety standards. These BFRs include chemicals, such as chlorine, bromine, and phosphorus. Currently, tetrabromobisphenol A (TBBPA) is among the most utilized flame retardants in the industry globally, which is classified as an endocrine disruptor. Endocrine disruptors are chemical compounds which inhibit the activities of natural hormones in the body, such as secretion, binding, transport, synthesis, action, or elimination responsible for maintaining reproduction, homeostasis, behavior, or development. Numerous concerns have been raised about human exposure to these disruptors, primarily because of the assumed detrimental effect they pose to human health. Owing to the high volume of production and potential human exposures, the toxicity of TBBPA has been investigated in a number of experimental studies. Research carried out on TBBPA has revealed less than 4% of its particles in dust are respirable and less than 10 µm can be absorbed from the lungs for systemic circulation after inhalation. However, based on the physicochemical properties of TBBPA, its absorption via dermal exposure is expected to be poor. Data from an in vitro study, conducted with human skin, showed that less than 1% of the administered dose was absorbed dermally. Human samples and rat strains have been studied for the metabolism and toxicokinetic action of TBBPA, which has confirmed that TBBPA can be absorbed from the gastrointestinal tract and rapidly eliminated after conjugation or Phase II metabolism to more water-soluble metabolites. TBBPA has low (F < 0.05) systemic bioavailability due to its extensive hepatic bio-transformation to glucuronides and sulfates, which are excreted from the liver predominantly with bile as a result of their high molecular weight. Knudsen’s group observed in their study that excretion was delayed only after a single dose of 1000 mg/kg bw, was orally administered, obviously because of the saturation of conjugation reactions. Other studies, showed that more than 95% of TBBPA administered orally is partially excreted as the parent compound and in feces it is eliminated in the form of metabolites within 3 days after a single dose with accompanying minute tissue retention or bioaccumulation, even at lower doses. ln human plasma, the expected half-life of TBBPA-glucuronide is estimated to be between 2 and 3 days.
  • 279
  • 27 Mar 2023
Topic Review
Mechanism of Abrasive-Based Finishing Processes
Various manufacturing industries have been using conventional procedures for finishing the components, such as grinding, honing, lapping, etc., to get the machining components’ desired finishing. However, these conventional procedures of finishing are restricted to very few geometries and cannot work on complex and intricate geometries as well as complicated profiles for finishing of high level, which is required while the operation of the component is in process. These limitations and restrictions in the finishing process have led the industries to develop advanced finishing procedures, known as “Abrasive flow machining (AFM)”. Advances in technology and refinement of available computational resources paved the way for the extensive use of computers to model and simulate complex real-world problems difficult to solve analytically. The appeal of simulations lies in the ability to predict the significance of a change to the system under study. The simulated results can be of great benefit in predicting various behaviors, such as the wind pattern in a particular region, the ability of a material to withstand a dynamic load, or even the behavior of a workpiece under a particular type of machining. 
  • 796
  • 29 Sep 2022
Topic Review
Mechanical Recycling of Thermoplastics
Plastic materials have gathered attention recently due to their omnipresence in the global economy. The transition towards a circular economy is the only way to prevent the environment from landfilling and incineration.
  • 330
  • 12 Oct 2023
Topic Review
Mechanical Properties of Sugarcane-Bagasse-Ash-Integrated Concretes
Leading sugar-producing nations have been generating high volumes of sugarcane bagasse ash (SCBA) as a by-product. SCBA has the potential to be used as a partial replacement for ordinary Portland cement (OPC) in concrete, from thereby, mitigating several adverse environmental effects of cement while keeping the cost of concrete low. The majority of the microstructure of SCBA is composed of SiO2, Al2O3, and Fe2O3 compounds, which can provide pozzolanic properties to SCBA.
  • 1.3K
  • 30 Oct 2022
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